Move command documentation into docs/ dir

This pull request moves the TomDoc for Sphero commands into docs/commands.md.

Some of the commands are currently better documented than others, but this will hopefully improve in the future.

The intention of this move is to build a structure that can be used in other Cylon/Artoo modules to make docs generation easier, as well as making it easier for end-users to find docs if they end up at this repo.

The structure I had in mind for docs generation was that each repo would have the following files:

- docs/commands.md
- docs/events.md
- docs/how-to-use.md
- etc

Not every adaptor emits events, and not every adaptor has commands, so there would be a bit of give-and-take with this format, but the idea is that a generator in the Middleman site for Cylon would, for each repo, pull out all of these files if they exist, convert them from Markdown to HTML, and then plug them into the [driver page](http://cylonjs.com/documentation/drivers/sphero/) on cylonjs.com.

This also means it's less resistance to updating the docs when you're adding or updating features in the adaptors, and when reviewing pull requests it's easier to request docs updates if features are changed. Then, when a new feature lands with appropriate documentation, the Middleman site can be quickly regenerated with the new content.

:paperclip: